In 1958 Britain discovered Cliff Richard; America found Joan Baez. It is not to disparage the man who once told the BBC that he was "the most radical rock star there has ever been" to say that Baez has done more to make the world a better place. Five decades on from her first performance she remains a political phenomenon as well as a musical one - endorsing for the first time in her life a presidential candidate, Barack Obama. She has one thing in common with his opponent: both were in Hanoi in December 1972, John McCain as a prisoner of war, Baez on a visit to North Vietnam that reflected her absolute opposition to America's war. Baez's commitment to peace and justice has always been outstanding: campaigning for civil rights in the American south, in Israel and Palestine, for Czech dissidents under communism, for Amnesty International and against the invasion of Iraq (where she lived briefly as a child). She is one of only four performers who were at both Woodstock in 1969 and Live Aid in 1985. Her new album, Day After Tomorrow, has returned her to the US album charts; she has just toured Britain. The protest songs of the 60s, she says, are needed again. Anyone who remembers listening to Baez the first time round - perhaps through a haze of student self-righteousness, joss sticks and funny cigarettes - knows that, however naive the simplicities of the world-view she has championed, she and her voice will be for ever on the side of the forces of light.